Extracting oil from underground reservoirs

ABSTRACT

Methods to extract oil from underground reservoirs are disclosed comprising pumping a gas comprising oxygen into the reservoir, causing combustion, and using the heat and pressure generated by the combustion to drive the oil through a well pipe to the surface. Systems for extracting oil from underground reservoirs are also disclosed comprising a gas compression system operable to pump oxygen from an oxygen source into the underground reservoir. The system has a supply pipe connected to the source of oxygen, a delivery pipe connected to the underground reservoir, a pump capable of pumping a liquid, a first tank with a first pipe and a second pipe, a second tank with a third and a fourth pipe and two pipe switchers operable to switch connections such that the tanks are swapped from a position between the supply pipe and the pump inlet and a position between the pump outlet and the delivery pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority as a Divisional application ofapplication Ser. No. 13/536,446, filed 28 Jun. 2012.

FIELD OF THE INVENTION

One or more embodiments of the present invention relate to self-primingpumps and applications thereof.

BACKGROUND

When air goes into a centrifugal pump, it can cause the pump to stoppumping water, because the centrifugal impeller cannot efficiently pumpair and suck water from a supply pipe. If the water source is far awayfrom the pump, it cannot efficiently pump water until the entire lengthof the source pipe is filled with water. A pump full of air may not beable to generate enough pressure difference to draw water into the pump.If some air bubbles are present in the long pipe, these air bubbles cancombine to form an air pocket which can stop the pumping of water.Therefore it is common practice to position centrifugal pumps close tothe water source (e.g., a river or lake). In the case of wells, the pumpis positioned at the bottom of the well to make the distance between thecentrifugal pump and the water source as short as possible.

There is also a risk, when putting an expensive diesel poweredcentrifugal pump a mile or more away from a house or farm, that the pumpcan be stolen at night. If the pump is electric, a long cable would beneeded extending from the house to the water source. The cableinstallation can be expensive, and it, too can be stolen. Further, ifmaintenance is required, it may be necessary to travel a long way,perhaps in the middle of the night, to correct a simple problem, forexample with fuel supply to the diesel engine.

Even with a pump positioned close to the water source, a “priming”operation is often required. In many pumps, this process is achievedmanually by pouring liquid into the pump through a priming port. Ifthere is a lot of air that must be purged from the supply line, eitherenough water must be added to completely fill the supply line, or thepriming operation may need to be repeated several times until all of theair is pumped out of the supply line. Typically, a small amount of aircan be “pumped” by entraining it into pumped water, but larger amountscan fill the pump with air again and cause it to stop pumping.“Self-priming” pump designs are also known, whereby the primingoperation is automated in some way. For example, in some installations,it may be possible to position the pump below the water level (eitherliterally submersed, or adjacent to the water supply but at a levelbelow the water surface). In these installations, gravity can providethe force required to keep the pump primed, even if the supply pipe isleaky, and the pump provides the additional force required to pump waterto a higher elevation and/or a distant location.

SUMMARY OF THE INVENTION

A pumping system is disclosed comprising a supply pipe; a delivery pipe;a pump capable of pumping a liquid; a first tank with a first top portand a first bottom port; a second tank with second top port and a secondbottom port; a first pipe switcher operable to switch connectionsbetween a first state and a second state, wherein the first statecomprises a connection between the supply pipe and the first top portand a connection between the delivery pipe and the second top port, andwherein the second state comprises a connection between the supply pipeand the second top port and a connection between the delivery pipe andthe first top port; and a second pipe switcher operable to switchconnections between the a first state and a second state, wherein thefirst state comprises a connection between the first bottom port and thepump inlet and a connection between the second bottom port and the pumpoutlet, and wherein the second state comprises a connection between thefirst bottom port and the pump outlet and a connection between thesecond bottom port and the pump inlet. The first state of the first pipeswitcher is contemporaneous with the first state of the second pipeswitcher, and the second state of the first pipe switcher iscontemporaneous with the second state of the second pipe switcher.

The first and second pipe switchers can each comprise two normally openvalves and two normally closed valves connected to a common actuator.The common actuator can comprise a solenoid and spring. The commonactuator can be a bistable actuator.

The first and second pipe switchers can each comprise a unitary valvebody with four ports, and can be combined into a single unitary bodywith a common actuator.

Sufficient fluid is initially present to fill the pump and the secondpipe switcher and to substantially fill one of the two tanks. At leastone level sensor in each tank can be provided. A control system canmonitor the level sensors and change the state of the switching valvessuch that the pump is always substantially full of fluid, even if thesupply pipe is empty of fluid.

A cooling system is disclosed comprising the above pumping system. Thesupply pipe is connected to the output of the evaporator of the coolingsystem, and the delivery pipe is connected to the input of the condenserof the cooling system.

A gas compression system is also disclosed comprising the above pumpingsystem. The supply pipe is connected to the source of gas to becompressed, and the delivery pipe provides compressed gas for use orstorage.

A system for pumping water from an underground reservoir is alsodisclosed comprising the gas compression system. The delivery pipe isconnected to a first well pipe going down into the underground reservoirand water is pushed up through a second well pipe to the surface.

A system for extracting oil is also disclosed. The gas compressionsystem is used to pump oxygen into an oil reservoir, and undergroundcombustion is used to drive heated oil to the surface. Optionally, asecond pumping system can be used to pump a combustible fuel into theoil reservoir.

A method for pumping water from an underground reservoir is disclosedcomprising pumping gas through a first well pipe into the undergroundreservoir using the above pumping system and pushing water up through asecond well pipe to the surface.

A method of heating an underground oil reservoir is disclosed comprisingpumping oxygen into the underground oil reservoir using the abovepumping system and causing combustion to take place in the undergroundoil reservoir. Optionally, a combustible gas or liquid is also pumpedinto the oil reservoir using a second pumping system. The heated oil canbe pushed through a well pipe to the surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the two tanks and a centrifugal pump.

FIG. 2 shows the centrifugal pump connected between the tank bottomswith supply and delivery pipes connected to the tank tops.

FIG. 3 shows the same tanks and pump with the supply and delivery pipesswapped and the connections to the pump swapped.

FIG. 4 shows a “magic pipe switcher” capable of making the pipe switchesbetween the state shown in FIG. 2 and the state shown in FIG. 3.

FIG. 5 shows details of the pipe connections for a magic pipe switcher.

FIG. 6 shows the pipe switcher valves connected to an actuator.

FIG. 7 shows details of the normally open and normally closed valves intheir “normal” position.

FIG. 8 shows the full set of four valves to make a magic pipe switcher.

FIG. 9 shows a complete pumping system with two magic pipe switcher andtwo tanks.

FIG. 10 shows a pumping system used as part of a cooling system with anevaporator and a condenser.

FIG. 11 shows a cooling system with a reversible pump and a single magicpipe switcher.

FIG. 12 shows a pumping system used to compress gas into a storage tank.

FIG. 13 shows a cooling system with an auxiliary gas storage tank.

FIG. 14 shows a pumping system used to drive compressed gas into anunderground reservoir to drive water to the surface.

FIG. 15 shows two pumping systems being used to pump oxygen and acombustible gas or liquid into an underground oil reservoir to heat theoil and drive it to the surface.

FIG. 16 shows a two-stage gas liquification system using two pumps andtwo condensers.

FIG. 17 shows a three-stage gas liquification system.

DETAILED DESCRIPTION

It must be noted that as used herein and in the claims, the singularforms “a,” and “the” include plural referents unless the context clearlydictates otherwise. Thus, for example, reference to “a valve” includestwo or more valves, and so forth. Embodiments are frequently describedfor centrifugal pumps pumping water, although it is understood that thepriming methods and devices disclosed herein apply to any pumptechnology requiring priming, and to the pumping of any liquid.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimit of that range, and any other stated or intervening value in thatstated range, is encompassed within the invention. The upper and lowerlimits of these smaller ranges may independently be included in thesmaller ranges, and are also encompassed within the invention, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the invention. Theterms “about” and “approximately” generally refers to ±10% of a statedvalue.

DEFINITIONS

As used herein, the term “centrifugal pump” refers to a pump having arotating impeller which increases the pressure of a liquid at the outerrotating edge relative to the axis. Typically, an inlet is mounted nearthe axis, and an outlet is mounted near the outer edge of the impeller.The pressure difference can then be used to pump fluid from the inlet tothe outlet.

As used herein the term “magic pipe switcher” refers to a valve assemblywith two inlets and two outlets, wherein the first inlet can beconnected to one of the two outlets and the second inlet can beconnected to the other outlet, and the connections are swapped when thevalve position is changed by a suitable actuator.

The present invention solves problems related to pump priming by addingtwo tanks and two “magic” pipe switchers so that a pump can draw air foras long as necessary until liquid arrives, and if the liquid is mixedwith some air, for example, due to air leakage in the supply pipe, thepump can pump liquid as if there were no air present. The pump can besituated anywhere convenient to the user.

There is one well-known limitation to pump positioning that applies toall liquid pumps, whether they require priming or not: it is notpossible to position a pump at a height above a water source thatexceeds a one atmosphere “head.” For example, when pumping fresh waterat sea level, a column of water 34 ft (10.4 m) high has a pressure atthe bottom of one standard atmosphere more than the pressure at the topof the column. Thus, if you try to pump water from a source located morethan 34 ft below the pump, the best you can do is to draw the water upto a height of 34 ft above its natural level. At that point, you willhave drawn all of the air out of the supply tube, and there will be avacuum in the pipe above that level. No pump can produce any force onthe column of water by “sucking” further on a vacuum. Therefore, anyself-priming pump must be positioned no higher than the height of acolumn of liquid corresponding to one local atmosphere of head pressure.

The present invention also enables new generations of cooling systemsand air compressor systems, employing the same magic pipe switchers tokeep the pump primed.

Referring to FIG. 1, in embodiments of the present invention, the inputof a centrifugal pump E with impeller F is always connected to a tank(either A or B) containing water, so the centrifugal pump E alwaysreceives water and can always pump water. In order to ensure that thereis always an available tank containing water, two tanks A and B areprovided, and a magic pipe switcher swaps which tank is connected to thepump input in a way that an empty tank is never connected to the inputas set forth below. The pump never stops pumping, because it is alwaysprovided with water to pump.

Referring to FIG. 2, the centrifugal pump E is shown sucking water fromtank A into pump inlet D and pumping it out through pump outlet C intotank B. Assume that tank A starts out nearly full of water. Tank A isconnected to supply pipe X and tank B is connected to delivery pipe Y.If there is no air in the system, then the tanks have no particularfunction and the water is pumped from supply pipe X to delivery pipe Y.

If air is present in the supply line, it will tend to collect in tank A,and the liquid level in the tank will gradually decrease. When tank A isalmost empty, even if no water has yet arrived via supply pipe X, tank Bwill be almost full from the water originally in tank A. Now the “magic”switching occurs, and the pipe connections are changed from thearrangement shown in FIG. 2 to the arrangement shown in FIG. 3. Bothpump connections and supply connections are reversed. Pump inlet D isconnected to tank B, and pump outlet C is connected to tank A Supplypipe X is connected to tank B, and delivery pipe Y is connected to tankA. Water is still pumped from supply pipe X to delivery pipe Y, but thetanks are reversed so that tank B is now connected on the input sidebetween supply pipe X and pump inlet D, while tank A is now connected onthe output side between pump outlet C and delivery pipe Y.

The switching function can be provided by the embodiment of a “magicpipe switcher” shown in FIGS. 4-8. FIG. 4 shows the complete assembly;FIG. 5 omits the valve actuator, so that the fluid flow paths can beseen more clearly; FIG. 6 shows just the valve actuator and valves, FIG.7 shows two magic pipe switchers in a unitary body driven by a singleactuator, and FIG. 8 shows just the four valves. All figures show thesame components in the same relative arrangement with reference lettersreferring to the same parts in each figure.) A magic pipe switcher Ncomprises four valves. Two valves L are normally open and two valves Mare normally closed. A strong spring and solenoid K are in opposition tocontrol the motion of the valves. When the solenoid K is activated, itpulls against the spring and opens the normally closed valves M andsimultaneously closes the normally opened valves L. There are fourports. Port G is always an input, port H is always an output, whileports I and J swap between input and output functions according towhether the solenoid K is activated or released. In the “normal”position with solenoid K released, port G is connected to port I, andport J is connected to port H. In the “active” position with solenoid Kactivated, port G is connected to port J, and port I is connected toport H.

FIG. 9 shows an embodiment of a complete system comprising a centrifugalpump E, two tanks A and B, and two magic pipe switchers N, the supplypipe X, and the delivery pipe Y. This assembly implements the tank andsupply switching functions described above. When the solenoids arereleased, supply pipe X is connected to tank A, and tank A is connectedto pump inlet D, while pump outlet C is connected to tank B, and tank Bis connected to delivery pipe Y. When the solenoids are activated,supply pipe X is connected to tank B, and tank B is connected to pumpinlet D, while pump outlet C is connected to tank A, and tank A isconnected to delivery pipe Y.

In some embodiments, tanks A and B further comprise level sensors.Various sensor types and locations can be used. In some embodiments, thesensors sense presence or absence of water. A two-sensor configurationcan be used with sensors near the top of each tank. Each sensor isprotected from splashing so that it detects water level in the tank andnot local turbulent flow. Starting with tank A mostly full of water andthe solenoids released, water is pumped from tank A to tank B,displacing the air of tank B. The water level in Tank B goes up, and airis pushed out. Tank A is refilled from supply pipe X which may containair, water, or a mixture of air and water. The air in tank B is pushedinto delivery pipe Y. Initially, the sensor at the top of tank A maysense the presence of water, but the sensor at the top of tank B doesnot sense the presence of water. As pumping proceeds, if there is air inthe supply pipe X, then at some point, neither sensor will detect thepresence of water.

After a time, as the liquid level rises in tank B, and its sensor willsense the presence of liquid. If the sensor at the top of tank A doesnot sense the presence of liquid (i.e., B and (not A)), a control systemactivates the solenoids K for both magic pipe switchers. The role oftanks A and B are now reversed. The pump now pumps water from tank Bwhich is full of water into tank A. But since tank B is connected tosupply pipe X and tank A is connected to delivery pipe Y, the pump isstill is pumping from supply pipe X to delivery pipe Y.

When the sensor at the top of tank A senses the presence of liquid, butthe sensor at the top of tank B does not sense the presence of liquid(i.e., A and (not B)), the control system releases the solenoids K forboth magic pipe switchers. The pump resumes water from tank A which isfull of water into tank B. The pump is still is pumping from supply pipeX to delivery pipe Y.

These two states can alternate until all air is removed from supply pipeX and Tank A. When all air is removed, the sensors at the top of bothtanks sense the presence of liquid (i.e., A and B) and the controlsystem does switch the state of the magic pipe switchers.

In the two-sensor embodiment just described, the alternation of statescan end with the solenoids either activated or released. The completelogic is given in Table 1. (Note that “unchanged” means that when theindicated state is reached, the solenoid is maintained in the previousstate.)

TABLE 1 Water at top of Water at top of tank A tank B Solenoid stateabsent absent unchanged absent present activated present absent releasedpresent present unchanged

In some embodiments, it is desirable to ensure that the fully primedpump state which can be maintained for extended periods of time occurswith the solenoids released. One way to ensure that the solenoids arealways released when the pumps are fully primed is to break the logicsymmetry by always releasing the solenoid whenever the sensor at the topof tank A senses the presence of water. The resulting logic is given inTable 2.

TABLE 2 Water at top of Water at top of tank A tank B Solenoid stateabsent absent unchanged absent present activated present absent releasedpresent present released

One characteristic of the logic shown in Table 2 is that after thesystem is fully primed, the magic switching valves will activate againas soon as enough air enters the system (e.g., from bubbles or leaks inthe supply pipe) that the sensor at the top of tank A no longer sensesthe presence of water. In some embodiments, an additional sensor isdisposed near the bottom of tank A. This sensor can be used to causeactivation of the solenoids only when the level in tank A drops belowthis lower level. Effectively, it is used to detect priming, but allowstank A to gradually fill with air after priming until the water levelfalls below the lower sensor, thereby reducing the number of time thatthe solenoids are activated to respond to bubbles and leaks. Thecomplete logic is shown in Table 3. States not listed cannot logicallyoccur. For example, if there is water present at the top of tank A, thenthere is always water present at the bottom of tank A. If there is nowater at the bottom of tank A, then there must be water present at thetop of tank B.

TABLE 3 Water at top of Water at bottom Water at top of tank A of tank Atank B Solenoid state absent present absent unchanged absent absentpresent activated absent present present unchanged present presentabsent released present present present released

The skilled artisan will recognize that there are other embodiments oflevel sensors and positions that can provide the same control functions.For example, sensors can be located near the bottoms of both tanksinstead of the tops. Rather than detecting the arrival of water at thetop of a tank connected to the delivery pipe to trigger a state change,one can detect the loss of water at the bottom of the tank connected tothe supply pipe. The skilled artisan will recognize that a similar tableof control logic can be made for sensors located near the tank bottoms.

Any suitable level sensing technology can be used. The presence sensorsused in the above embodiments can be, for example, mechanical,electrical, optical, acoustic, ultrasonic or radar. Sensors whichprovide a digital or analog level indication can also be used, based on,for example, mechanical, electrical, optical, acoustic, ultrasonic orradar measurement techniques. Pressure sensors can be used as levelsensors. The skilled artisan will recognize that the control logic canvary to exploit particular measurement technologies. For example, apressure sensor at the bottom of a tank can be used to indicate tankfluid level based on the head of liquid. In this way, one sensor canreplace the functionality of both an upper level and a lower levelsensor.

In some embodiments, to reduce energy use further, the magic pipeswitcher can have a holding pin. When the solenoid is activated, a pinis pushed by a spring such that the pin holds the valves in position,the power to the solenoid can be removed, and no electricity is requiredto hold the solenoid in position. When the control system decides thatthe solenoid should be releases, a signal is sent to a separate smallpin actuator to pull the pin out so that the main solenoid spring canreturn the solenoid to the released position. The pin actuator onlyneeds to be activated for a brief time interval sufficient to pull thepin. To reduce the power required for the pin actuator, the mainsolenoid K can be reactivated briefly to relieve the spring force on thepin, so that very little force is required to pull the pin.

In some embodiments, a bistable valve actuator can be used instead of asolenoid opposed by a spring. In these embodiments, both the “activated”and “released” states are inherently stable positions, and power must beapplied only to move the actuator from one state to the other.

In any embodiments not requiring power to hold one position of the magicpipe switcher, the control system need not return the actuator to thereleased state when the pump is fully primed.

In some embodiments, the magic pipe switcher N can be activated by hand.A user can close and open the valves manually via a handle. Theseembodiments can be cheaper, and may be adequate for applications wherethere is only a need to use the magic pipe switcher briefly on startup,and the supply of water is continuous once the pump is primed.

In some embodiments, the two magic pipe switchers can be integrated asone unit having eight input/output pipes and eight valves operated by asingle actuator of any of the types described above. The magic pipeswitcher can be made in many different forms and in numerous versions.For example, the magic pipe switcher can be made as four valves, eachhaving its own actuator, where the electronic controls provide thecorrect sequencing.

In some embodiments, a magic pipe switcher is integrated into a singlecylindrical device. A sliding cylinder can have two cross holes. One endof each of the cross holes connects to channels in the walls which arealways connected to ports G and H respectively. The other end would havechannels that reverse the connection as the cylinder move between twooperating positions. For example, the two cross holes could be bothdisplaced vertically and rotated at an angle with respect to each other.One channel could then be horizontal, while the other has a longer patharound the horizontal channel. The net functionality is essentiallysimilar to an electrical double-pole-double-throw switch used to reverseelectrical connections. In some embodiments, two of these integratedmagic pipe switchers can be integrated into a single cylinder with asingle actuating mechanism.

In some embodiments, the two tanks A and B, the centrifugal pump, andthe two magic pipe switchers can be integrated all together in one boxto make one compact system with only two fluid connections, one forpumping and the other for suction.

In some embodiments, the tanks A and B further comprise one-way checkvalves at the top and bottom of the tanks. The tank connected to theoutlet of the pump will generally contain higher pressure than the tankconnected to the inlet, and it can be advantageous to prevent backflowfrom the delivery pipe Y and into the supply pipe X when the roles ofthe tanks are switched by the magic pipe switcher. The check valvesensure that flow is only possible out of the supply pipe and into thedelivery pipe. Building codes may require such check valves to protect awater supply from back contamination. The check valves also ensure thatno progress is lost in the net flow of water from the supply pipe to thedelivery pipe during tank switching events. After switching, excesspressure in the tank newly connected to the pump inlet is relieved byforcing fluid through the pump to the tank newly connected to the pumpoutlet. The pump then continues to decrease the pressure in the tank onthe supply side and increase the pressure in the tank on the outlet sideuntil the pressures are such that all check valves are open and pumpingout of the supply pipe and into the delivery pipe can resume.

EXAMPLES

Embodiments of self-priming pumps have been described above in thecontext of water pumps, generally, where the source of water is locatedno more than about 10 m below the pump location. Such pumps can be usedfor any general-purpose water pumping application including but notlimited to drinking water supply, sump pumps, draining of floodedspaces, firefighting, swimming pool draining and filling, industrialwater supply, sanitary water supply, irrigation, and so on. Otherapplications are also possible as exemplified below.

Example 1 Gas Compressor

In some embodiments, the pump can be used to compress a gas. FIG. 12shows a tank S for storage of compressed air or gas. The tank S isconnected to the delivery pipe Y. A pump liquid is cycled between tank Aand tank B in order to raise the pressure of successive volumes of gasand pump these volumes into the delivery pipe Y and tank S. Check valvesare used to ensure that no backflow occurs as tanks A and B are swapped.A pressure switch on tank S can be used to turn the pump off when adesired pressure is reached and to turn the pump back on when thepressure drops below a lower set point.

The liquid pumping fluid is repeatedly cycled between tanks A and B, andthe self-priming ability of the pump is used to effectively pump the gasto compress it on each cycle. The liquid can be selected to resist hightemperature and freezing. An antifreeze solution (e.g., a solution ofethylene glycol) or a hydrocarbon or silicone oil can be used.

The fluid volume is chosen so that one of the tanks is full of liquidand the other one is partly empty at the start of a cycle. Pumpingproceeds as usual until the liquid reaches the top of the tank connectedto pump output, and substantially all of the gas has been pushed out ofthe tank. The controller receives a signal from a sensor, the state ofthe magic pipe switchers is changed, and the direction of the pumping iseffectively changed so that the pump output is connected to the emptytank, and the pump input is connected to the full tank. Gas is alwayssucked from the supply pipe X and pushed into the delivery pipe Y. Checkvalves ensure that there is never any backflow.

Centrifugal pumps generate pressure by rapid rotation of a volume offluid to develop a pressure increase from the center of rotation to theperiphery. The pump inlet is directed near the axis of rotation and thepump outlet is on the periphery. Gas compression applications oftenrequire high pressures. Typical compressed gas storage tanks store gasat 2000-3000 psi and more. In general, it is possible to increase thepressure difference between the inlet and outlet of a centrifugal pumpeither by increasing the angular speed of rotation of the pump or byincreasing the diameter of the impeller or both. Most centrifugal pumpsare, however, limited as to how much pressure increase can bepractically achieved. Excessive speed at the outer edge of an impellercan result in cavitation in the fluid which can both reduce pumpefficiency and damage the impeller surface. Higher pressures can beachieved by connecting a set of centrifugal pumps in series. Optionally,the set of pumps can be driven on a common shaft by a common drivemotor, and the fluid connections can be made integral to a commonhousing. Multistage pumps of this type are available commercially, forexample, from Dickow Pump Co. (Marietta, Ga.) and V-Flo Group (Shenyang,China). Output pressures of at least 3800 psi are available. Multistagepumps can be used in embodiments of the present invention.

Example 2 Deep Water Wells

In some embodiments a self-priming pump can be used to pump water fromgreat depths without using a submersible pump at the bottom of the well.The pump is used to pump a gas in a manner similar to that of Example 1.The arrangement is shown in FIG. 14. The pump system is located at theearth surface, and the delivery pipe is connected to a pipe V extendingdown to the water reservoir. A well pipe W provides a path for the waterto rise to the surface. As long as the water reservoir is contained in aclosed region that can be pressurized, the pump can be used to raise thepressure in the closed region to drive water up a well pipe whose inletis positioned below the water surface. High pressures may be required,but since all pressures are above atmospheric, there is no limitation ondepth from which water can be pumped.

Example 3 Carbon Sequestration

In some embodiments a self-priming pump can be used to pump CO₂ intounderground reservoirs. The pump is used to pump CO₂ in a manner similarto that of Examples 1 and 2. Geological formations with enormouscapacities exist that can be safely used to sequester extremely largevolumes of gas.

Example 4 Cooling System

In some embodiments a self-priming pump can be used to operate arefrigeration or cooling system as shown in FIG. 10. The pumpconfiguration is the same as that shown in FIG. 9 except that theevaporator P of the cooling system is connected through the supply pipeto port G of the upper magic pipe switcher N and the condenser Q of thecooling system is connected through the delivery pipe to port H of theupper magic pipe switcher. A fine tube or evaporation control valve R islocated between the condenser and the coils of the evaporator. The pumpis used to pump a gas in a manner similar to that of Example 1, exceptthat the gas to be compressed is a refrigerant gas such as ammonia orFREON®.

In some embodiments of cooling and refrigeration systems, tanks A andtank B are tapered at the top, so that all gas in the tank connected tocondenser Q is pushed out of the tank when the liquid reached the top ofthe tank, thereby maximizing overall efficiency of the system.

In some embodiments, a pump E having reversible pumping direction can beused. With a reversible pump, the configuration of FIG. 11 can be usedwith a magic pipe switcher N only at the top of tanks A and B. Thecontrol system can then switch the pumping direction at the same timethat the magic pipe switcher state is changed.

Cooling systems according to these embodiments are especiallyadvantageous for large systems such as those used in ships, warehouses,large buildings and the like where efficiency, energy savings, reducedmaintenance costs, and ease of maintenance are particularly important,but the methods can be beneficially applied for cooling systems of anysize.

In some embodiments, the cooling system can have a tank S for storingcompressed gas connected to the delivery pipe as shown in FIG. 13. Anadditional small compressor U can further compress the gas and pump itinto the condenser Q. A check valve can be placed at the inlet to tank Sto prevent backflow to the main pump.

This combination can enable a small secondary compressor to operate alarge cooling system from an already compressed gas with cost and energysavings.

Example 5 Extracting Oil from Depleted Oil Fields

Abandoned or depleted oil fields can contain enormous amount of oil assemi-solid rock or thick oil sludge, hundreds of meters below thesurface. To lift this type of oil from such wells, it must be convertedit into a runny liquid by heating and then the pressure above thereservoir of oil must be increased to drive the oil to the surface. Heatcan be provided by underground combustion. Oxygen (or air) can be pumpedinto the underground reservoir. If there is sufficient volatilecombustible material in the reservoir supplying oxygen can be sufficientto start combustion and the resulting heat and pressure can drive oil tothe surface. In some reservoirs the residual oil may not readilycombust, and additional fuel must be supplied, at least until sufficientheat is generated to vaporize some hydrocarbon fuel.

FIG. 15 shows an exemplary embodiment using two pumps equipped withtanks and magic pipe switchers. One pump is used to pump oxygen usingthe methods given in Example 1 deep into an abandoned or depleted oilreservoir. A second pump is used to pump a gas or liquid capable ofreacting with oxygen to make a combustion reaction. The combustionreaction, deep inside the oil well, can generate super-heated gas and atremendous rise of pressure inside the oil well. The heat can melt thesemi-solid oil and converts it into a lower viscosity liquid, and themassive pressure can push the oil up the oil well pipe.

Any combustible gas can be used. In some embodiments a gas or liquidsuch as a hydrocarbon gas is selected which has gaseous products ofcombustion (e.g., CO₂) to help increase the pressure in the oil field.

Initially, the flow of oil to the surface may be small, but as pressurebuilds inside the oil well, the recovery rate can increasesubstantially; it is estimated that about 7-10 barrels of oil can berecovered for every barrel-equivalent used to fuel the undergroundcombustion. The useful life and total extractable oil from old oilfields can be extended dramatically by these methods.

Pumping oxygen or air into an oil reservoir and then starting combustionis a very good method for extraction of oil from abandoned oilreservoir. However, in some embodiments, any available gas such as CO₂or N₂ or a gas mixture can be used without initiating combustion topressurize an oil reservoir and push oil to the surface through a wellpipe.

In some embodiments, the reactants necessary for combustion are allpumped into the oil reservoir from the surface. Such reactants can betwo or more gases, a mixture of one or more gases and one or moreliquids, or a mixture comprising gases and/or liquids with powders. Anysuitable mixture can be used that can be ignited in the reservoir togenerate heat and pressure in the oil reservoir.

In an oil reservoir with a plurality of abandoned oil wells, some wellscan be used to pump oxygen into the reservoir and other wells can beused to extract the oil. No new wells are required—only a few pumpingsystems.

Example 6 Gas Liquification

Gas liquification can be accomplished by multi-stage compression andcooling. For example, fuel gases such as methane are typically liquefiedfor storage and transport by railroad or truck tanker or by ship. FIG.16 shows a two-stage compression system with two condensers Q and twopumps. In FIG. 16, the second pump U is shown as a small auxiliary pumpsuch as a piston pump, although it can also be another pump of the typedescribed in Example 1. The liquefied gas is being shown loaded onto aship. FIG. 17 shows a three-stage gas liquification system using threepumps of the type described in Example 1, together with threecondensers.

It will be understood that the descriptions of one or more embodimentsof the present invention do not limit the various alternative, modifiedand equivalent embodiments which may be included within the spirit andscope of the present invention as defined by the appended claims.Furthermore, in the detailed description above, numerous specificdetails are set forth to provide an understanding of various embodimentsof the present invention. However, one or more embodiments of thepresent invention may be practiced without these specific details. Inother instances, well known methods, procedures, and components have notbeen described in detail so as not to unnecessarily obscure aspects ofthe present embodiments.

What is claimed is:
 1. A method of heating an underground oil reservoircomprising pumping a gas comprising oxygen into the underground oilreservoir, and causing combustion to take place in the underground oilreservoir.
 2. The method of claim 1, further comprising pumping acombustible gas or liquid into the oil reservoir.
 3. A method ofextracting oil from an underground oil reservoir, comprising heating theunderground oil reservoir by the method of claim 1, and furthercomprising using the heat and pressure generated by the combustion todrive oil through a well pipe to the surface.
 4. A method of extractingoil from an underground oil reservoir, comprising heating theunderground oil reservoir by the method of claim 2, further comprisingusing the heat and pressure generated by the combustion to drive oilthrough a well pipe to the surface.
 5. The method of claim 1, whereincombustion takes place spontaneously when oxygen contacts oil in theunderground oil reservoir.
 6. A system for extracting oil from anunderground reservoir comprising a first well pipe, a source of oxygen,and a first gas compression system, wherein the first gas compressionsystem is operable to pump the oxygen from the source into theunderground reservoir, wherein combustion takes place when the oxygencontacts oil in the underground reservoir, and wherein the heat andpressure generated by the combustion is sufficient to drive oil throughthe first well pipe to the surface.
 7. The system of claim 6, furthercomprising a second gas compression system configured to pump acombustible gas or liquid into the underground oil reservoir.
 8. Thesystem of claim 6, further comprising a second well pipe, wherein thefirst gas compression system is configured to pump the oxygen from thesource into the underground reservoir through the second well pipe. 9.The system of claim 7, further comprising a second well pipe, whereinthe first gas compression system is configured to pump the oxygen fromthe source into the underground reservoir through the second well pipeand the second gas compression system is configured to pump thecombustible gas or liquid into the underground reservoir through thesecond well pipe.
 10. The system of claim 6, wherein the first gascompression system comprises a supply pipe connected to the source ofoxygen; a delivery pipe connected to the underground reservoir; a pumpcapable of pumping a liquid; a first tank with a first pipe connected tothe first tank at the upper end of the first tank and a second pipeconnected to the first tank at the lower end of the first tank; a secondtank with a third pipe connected to the second tank at the upper end ofthe second tank and a fourth pipe connected to the second tank at thelower end of the second tank; a first pipe switcher operable to switchconnections between a first state and a second state, wherein the firststate comprises a connection between the supply pipe and the first pipeand a connection between the delivery pipe and the third pipe, andwherein the second state comprises a connection between the supply pipeand the third pipe and a connection between the delivery pipe and thefirst pipe; and a second pipe switcher operable to switch connectionsbetween a first state and a second state, wherein the first statecomprises a connection between the second pipe and the pump inlet and aconnection between the fourth pipe and the pump outlet, and wherein thesecond state comprises a connection between the second pipe and the pumpoutlet and a connection between the fourth pipe and the pump inlet;wherein the first state of the first pipe switcher is contemporaneouswith the first state of the second pipe switcher, and the second stateof the first pipe switcher is contemporaneous with the second state ofthe second pipe switcher.